Role of neuroimaging in the presurgical evaluation of epilepsy

A significant minority of patients with focal epilepsy are candidates for resective epilepsy surgery. Structural and functional neuroimaging plays an important role in the presurgical evaluation of theses patients. The most frequent etiologies of pharmacoresistant epilepsy in the adult population are mesial temporal sclerosis, malformations of cortical development, cavernous angiomas, and low-grade neoplasms. High-resolution multiplanar magnetic resonance imaging (MRI) with sequences providing T1 and T2 contrast is the initial imaging study of choice to detect these epileptogenic lesions. The epilepsy MRI protocol can be individually tailored when considering the patient's clinical and electrophysiological data. Metabolic imaging techniques such as positron emission tomography (PET) and single photon emission tomography (SPECT) visualize metabolic alterations of the brain in the ictal and interictal states. These techniques may have localizing value in patients with a normal MRI scan. Functional MRI is helpful in non-invasively identifying areas of eloquent cortex.Developments in imaging technology and digital postprocessing may increase the yield for imaging studies to detect the epileptogenic lesion and to characterize its connectivity within the epileptic brain.